1. Field of the Invention
The present invention relates to a light emitting device which is provided with a light emitting element and a phosphor, and which is configured to emit light, and a method for manufacturing the light emitting device.
2. Description of the Related Art
A known conventional light emitting device, which is provided with a light emitting element and a phosphor, is configured in the following manner, for example. A lead frame, which is provided with a concave section, is used to mount a light emitting diode (LED), which is the light emitting element, on a bottom surface of the concave section of the lead frame. The phosphor is mixed with a transparent resin, and the concave section is fully filled with this phosphor-containing resin so that the resin covers the LED. The phosphor is designed to absorb light emitted from the LED, and is designed to convert the light into light having a different wavelength. Among light emitting devices of this configuration, there is one in which a blue LED is used as the LED and the phosphor configured to convert wavelength of the light for the blue LED into that for yellow is used, for example. Such a light emitting device enables white light to be emitted on a light emission observation surface by mixing the blue light and the yellow light. Meanwhile, in another light emitting device, a near ultraviolet LED is used as the LED and the phosphor configured to convert wavelength of the light for the near ultraviolet LED into those for three colors of red, green, and blue is used. Such a light emitting device enables white light to be emitted on a light emission observation surface by mixing the colors emitted from the phosphor.
However, in these light emitting devices, depending on the shape of the light emitting element, uneven light emission is caused due to a difference in light intensity of the blue light or the near ultraviolet light emitted from an upper surface side or a side surface side of the light emitting element. For example, as shown in FIG. 1, a light emitting device 800 configured in the following manner will be considered. A light emitting element 80 is mounted in the device, and phosphor-containing transparent resin 81 fills around the device while contacting and covering the device. The light emitting element 80 has a structure in which the light intensity is the highest in a direction directly above the blue LED or the near ultraviolet LED. When the light emitting device 800 is viewed from a light emission observation surface 1, an overhead section 2 of the light emitting element 80, in which the blue LED or the near ultraviolet LED is used, looks blue or violet due to the blue light or the ultraviolet, and a sounding section 3 looks white. Accordingly, this device causes color shading. As shown in FIG. 2, there may also be a case in which the light intensity is the highest in a lateral direction and an obliquely downward direction depending on a shape of a light emitting element 90. Consideration will be given for a light emitting device 900 of a configuration in which such a light emitting element 90 is mounted, and in which phosphor-containing transparent resin 91 fills around the device while contacting and covering the device. In a case where the light emitting device 900 is viewed from a light emission observation surface 1, an overhead section 2 of the light emitting element 90, in which the blue LED or the near ultraviolet LED is used, looks white, and a surrounding section 3 exhibits a color in a blue to ultraviolet zone. Accordingly, this device cause color shading.
As a light emitting device with which such color shading can be eliminated, light emitting devices as disclosed in Japanese Patent Publication No. 2004-111882 (hereinafter referred to as “Patent Document 1”) and in Japanese Patent Publication No. 2004-349647 (hereinafter referred to as “Past Document 2”) are known. The light emitting device disclosed in Patent Document 1 has a following configuration. After the light emitting element is mounted on the concave section of the lead frame, first phosphor-containing transparent resin having a low phosphor concentration is filled up to a position of an upper surface of the light emitting element. Second phosphor-containing transparent resin having a high phosphor concentration is disposed on the first phosphor-containing resin. A value, which is obtained by multiplying an optical path length reaching an upper surface of the second phosphor-containing transparent resin by the concentration of the phosphor, is maintained to be constant. Thereby, color shading is reduced. On the other hand, in the light emitting device disclosed in Patent Document 2, a phosphor unit is disposed on a plane of an optical member located inside the light emitting device, the plane facing the light emitting element. In addition, in-plane intensity distribution of the phosphor concentration is provided within the plane. Thereby, color shading is reduced.
However, in the light emitting device disclosed in Patent Document 1, there is a case where a position for fixing the light emitting element to a concave section of a base is displaced when the light emitting element is mounted on the concave section of the base. In this case the methods of forming the phosphor-containing resin, which corresponds to the respective conventional techniques described above, likely induce displacement of a layout between the light emitting element and the phosphor-containing resin. A problem, which may occur as a consequence, is that color shading cannot be reduced. Moreover, as in the light emitting device disclosed in Patent Document 2, in a case where the device is configured so that the light emitting element and the phosphor-containing resin are located apart from each other, it is necessary to consider spread of the light emitted from the light emitting element as well. Accordingly, there is a problem that it is technically difficult to control the in-plane intensity distribution for the spreading radiation or for the position to which the light emitting element is fixed.